Induction radio system



vs sheets-sheet 1 W. S. HALSTEAD INDUCTION RADIO SYSTEM Filed March 24, 1945 Feb. 5, 1946.

ATTORNEY Feb. 5, 1946. (w. s. HALsTEAD INDUCTION RADIO SYSTEM Filed March 24, 1945 3 Sheets-Sheet 2 mD 524s/ ATTQRNEY Feb. 5, 1946. w. s. HALsTr-:AD 2,394,444

' INDUCTION RADIO SYSTEM Filed March 24, 1945 s sheets-sheet s WILLIAM S. HALSTEAD INVENTOR Patentedfcb. 5, 1946 UNITED STATES lPATENT UFFICI?.

mesne assignments, to Farnsworth Television & Radio Corporation, Fort Wayne, Ind., a corporation of Delaware Application March 24, 1945, Serial N0. 584,588

Claims. -(Cl. 179-63) This invention pertains to radio communications, and more particularly to a distribution system for distributing one or more radio signals or programs to at least one receiver. In accordance with the invention, each receiver is preferably provided with a separate loop antenna disposed within or adjacent an internal master loop included in the receiving portion of the system.

More specifically, the invention provides a plurality of transmittersoperating on diilerent frequencies with varying types of intelligence impressed on the various transmitters. The transmitted intelligence is inductively impressed upon a distribution network, which intelligence is reimpressed upon an external loop disposed adjacent the distribution network and coupled to a plurality of receivers, the output of said plurality of receivers being coupled to a plurality of complemental transmitters, and the output of said transmitters being coupled to a master internal loop. In operation, the master internal loop provides a concentrated signaling field within the confines thereof, so that one or more portable receivers may be disposed within the confines of the loop, or adjacent thereto, for reception of signal intelligence from the plurality of transmitters. The portableA receivers preferably include means for selecting any one of a number of programs, and said portable receivers may, if desired, have their operation initiated by the insertion of a coin in a coin-controlled timing mechanism which places the receiver in operation.

The system of the invention is particularly adapted for use in signal receiving areas which may be either stationary or movable. The distribution network may be conventional wayside conductors, such as rails, telegraph lines, telephone lines, power circuits or other signal conducting media; or conductors may be installed to supplement the ordinary wayside wires where the wayside conductors are not disposed for adequately meeting the requirements of the system. In the present specification and appended claims the term wayside wires" may therefore be understood to include any functionally equivalent conductors.

A particular application of the invention is used in conjunction with moving vehicles, such as a railway coach or omnibus, so that the signals which are impressed from the transmitters upon the distribution network may be picked up by the external loop disposed on said railway coach or omnibus, and redistributed either by amplincation or retransmission to a master internal loop installed within the railway coach or omnibus. In this manner, a portable receiver or a plurality of portable receivers may be used Within the moving vehicle for selectively receiving any of the signals impressed upon the distribution network from the transmitting portion of the system.

One of the primary objects of the invention is to provide a radio distribution system in which a plurality of transmitters are coupled to a distribution media for distributing signal energy which is to be received by receivers having the output thereof impressed upon a master receiving loop, so that a plurality of portable receivers may be disposed within the master receiving loop which provides the concentrated signaling field which is utilized by said plurality of portable receivers.

One object of this invention is to provide a radio program distribution system in which a, number of transmitters. each modulated by a separate intelligence bearing signal, for example news, music, or the program of a broadcast network, are all coupled, via a common line coupling unit, to the wayside wires previously mentioned, so that a plurality of carrier currents, each bearing a distinct program, are transmitted along such wayside wires, from which they may be picked up by suitable devices located upon a vehicle proceeding alongside such Wires.

Another object of this invention is to provide a vehicle receiving and distribution system for radio programs, in which a single pickup loop is inductively coupled to wayside wires carrying programs upon carrier current frequencies and the output of the loop is fed to a number of receivers, each tuned to a separate carrier frequency, the outputs of all the receivers being retransmitted upon separate frequencies and reradiated by a common antenna, such as a loop of the concentrated induction field type, so as to supply the reradiated programs only over the limited area embracing the vehicle itself.

Yet another object of this invention is to provide radio program service in a moving vehicle, for use by the individual passengers therein, including a number of compact receivers distributed throughout the vehicle and capable of lndividual control so as selectively to receive a desired program.

Still another object of this invention is to provide individual radio receivers of a relatively cheap, simple and compact construction which may be operated by passengers in a vehicle upon insertion therein of a coin, so that such receivers can constitute a source of revenue.

Another purpose of this invention is to provide a radio program distribution system in which vehicles proceeding along highways or railroad tracks having electrical conductors adjacent thereto, such as telegraph, telephone, or other signaling circuits, may be enabled to pick up radio programs distributed over such wayside wires, -thereby reducing the necessity of employing upon the vehicle sensitive receivers capable sired radio programs with suiiicient clarityand .A

consistency.

Yet another purpose of this invention is to provide a radio program distribution adapted for supplying programs t0 a number of moving vehicles without the necessity of any vehicle being equipped with sensitive and comparatively long range radio receivers, whereby operation of the receiving devices upon the various vehicles is greatly simpliiied and reception of high quality programs is facilitated.

Still another purpose of this invention is to supply a carrier current transmission system whereby traic instructions and the like may be readily communicated to the operators of moving vehicles such as buses or railroad trains, without the employment of radiated energy effectively covering a large area, the energy being guided along wayside. wires near which the vehicle is traveling.

Fig. 5 shows one form of the roof-moimted antenna which may be employed as the external loop of the receiving system.

Fig. 6 is a front elevation of an illustrative form of individual receiver which may be used with the present invention.

Referring to the drawings, and more particularly to Fig. 1, there is shown a block diagram of the system in which are illustrated three transmitters I0, II, and I2, operating on frequencies FI,.F2, and F3, respectively. 'Ihe input of transmitter I0 connects to a news program source I4, that of transmitter II, Ato a music program source I5 and transmitter I2 to a broadcast network program source IB. While there are indicated only three transmitters with their respective programs, the system can readily include additional transmitter units operating on separate frequencies with their corresponding program units, which may include other music or broadcast network programs.

The above-mentioned transmitters are coupled through a line coupling unit I8 to a radiofrequency transmission line 20, said line usually ex- An additionai object of this invention is to provehicle to a number of individual radio receivers ,l provided with program selecting devices and optionally with coin controlling and timing devices.

Other objects and advantages of this invention may be and may become apparent to those skilled in the art from the following detailed description, and it is to be understood that the illustrations presented herein are merely representative of the invention and that modications may be made therein without departing from the spirit of the subjoined claims.

In the drawings:

Fig. 1 is a block diagram of one form of the system showing the transmitters disposed adjacent a distribution media or' network, and a receiving system disposed to receive signals picked up from the distribution network, with the output oi the receivers coupled to an antenna loop providing a concentrated signaling eld within the loop so that one or more local receivers may be disposed within or adjacent said concentrated signaling ileld.

Fig. 2 is a perspective view of one form ofA the individual receiver having a receiving loop connected thereto, which loop is used as a means for supporting the receiver.

Fig. 3 is a partly schematic and partly block diagrammatic representation of one form of the receiving system showing the individual receiver loop disposed adjacent the masterinternal loop.

Fig. 4 is a schematic diagram of one circuit tending for a distance of several hundred feet parallel to and in close proximity to wayside wires ril which normally extend along a highway or railroad right of way. The transmission line v2li is terminated to ground through a suitable terminating unit, shown in this instance as a variable resistor 23 and a capacitor 24, to inhibit formation of standing waves o'n theline with consequent likelihood of appreciable space radiation of radio wave energy. The combined induction and radiation elds surrounding transmission line 20 extend laterally for a substantially limited effective signaling distance usually less than M21, where x is the wavelength in meters of the carrier signal, as is more fully described in my copending application Serial No.

514,094, filed Dec. 13, 1943. The carrier signalV induced along wayside Wires 2l in turn establishes combined induction and radiation fields about the WiresV 2|, extending laterally on each side of the wayside wires for an effective signaling distance DI, as shown on the drawings.

A loop 2l normally placed in a vertical plane parallel 'to the Wayside wires and outside of the body of a vehicle, such as railway coach or motor bus 28 is connected through loop coupling unit 3U to receivers 3|, 32, and 33, these receivers being tuned to frequencies FI, F2 and F3, respectively, as indicated by legend, andha'ving their output circuits connected respectively to the signal input circuits of transmitters 36, 31, and 38, these latter mentioned transmitters being tuned to frequencies F4, F5, and F6, respectively.

The output circuits of transmitters 36, 31 and 38 are fed to coupling unit 39 which is in turn connected to the loop 4I inside of the railway coach or bus 28. Loop antenna 4I may extend around the inside walls of the vehicle at slightly below ceiling level or at any desired height from the floor.

With the system .just described, a simple receiving set provided with a loop antenna responsive to the combined induction and radiation elds surrounding loop 4| will pick up any of the programs injected inside of the vehicle, when the set is tuned -to the proper frequency, such as Fl, F5, or-FS, or to FI, F2, and F3 if the same carrier frequencies originating at the transmitform of the coin\ controlled switching means for controlling operation of the receiver.

ters I0, II, and I2 are injected into the interior of the vehicle. The vehicle 28 is indicated with doiiiieseatsmangedoneachsideotthecenter Areceiverinwhichcoin-sctuatedswitch'liis aille,suchasthedualseat Ori therear apartoperatesincombinationwithpickuploop oieadiseatoratanyothersuitablelocationmay llandmaybetunedbytheusertothedesired be positioned individual receiving sets such as frequencies such as Fl, Fl and Fl by capacitors M so thet passenger or person seated in one 5 M, ",and whichareselectivelyconnectedln oitheseats,suchasll,mayhavaccesstothere the tuned circuit ot.which loop I3 is a part,by ceiving set directly in front o! his seat, such as program selector switches l1, l, and il respecu, tively. As an example, switch l1 connects calig. 2 illustrates one form of the receiving set pacitor il across the loop Il to receive a news with a loop I3 and coin-operated radio receiver 10 program on frequency F4. Alternatively, switches Mincombination. Thereceiverumayoonsist Ilandmaybeactuatedtoconnectcondensers o! a compact case Il o! plastic or other suitable or respectively, across loop II to tune the material, to hold the various radio parts and receiver to other frequencies, for example, ireeoin and the case is supported by a quencies on which are broadcast music or network iiexible plastic covered loop I3. The equipment l5 programs. The switching arrangement may be simporting loop Il, as shown, positions the unit oi well-known interlocking type, not illustrated, on the rear of the seat ll in the vehicle. The so that when the selected switch is pressed the receiving set is provided with an opening 54 in other switches are automatically restored in their which a coin may be inserted and a plunger 55, oilm position. A radiofrequency rectiner 1I, such which is pressed downward after the coin is in# as a selenium detector of ilxed-adjustment type, sei-ted, allowing the receiver to be placed in operconverts the radiofrequency signal to audio freation either for the duration of the trip or arquency, the audio frequency signals being applied ranged so that a mechanical timing device is set to receiver output terminals 15 and transducer II, in operation by the movement of the plunger $5 connected therewith. to provide a predetermined unit of time during The coin-actuated switch 1i may be o! such a which the receiver is operative, such timing dedesign that by inserting the proper coin, theradio vices being well known in the coin machine receiver will operate ior the duration of a trip, art. l or it may consist of a mechanical escapement de- Program selector push-buttons or switches such vice, or the like, whereby the pressing of lever 55 as l1 may also be provided to permit selection 30 allows the radio receiver to operate for a. predeof news, music or broadcast network programs termined length of time before restoring it to the by the user. oiF' position, such devices being well known in The door Il, provided with a transparent winthe coin machine are do'. may be arranged so that it is normally Fig. 4 shows one `arrangement of transducer 55 locked in the closed position and is unlocked when in which contacts 13 of com actuated switch 1i, the above-mentioned coin is inserted and pluns- Fig. 3, normally forms a short-circuit across er Il is operated, as may be accomplished by env transducer 59, and are opened when the coin is well-known mechanical amusement, thereby inserted. The terminals 1l, Fig. 4, are identical providing access to a transducer unit 59. such with terminals 1s, shown in Fig. 3. as an earphone, connected t0 the receiver proper 40 Fig, 5 is an illustrative showing of one possible by the conduotin col'd arrangement of receiving loop 21 on the top of a It will be oblved tout by the use of individual vehicle 28, such as a railroad coach, in which the earpiece transducer a user may receive an indiloop may consist of rigid copper tubing held in vldllllly-Selcctcd prom Without causing intcl'- place at intervals by stand-011' insulators, such as ference with or dlsturbin a person in an adjoinplastic or ceramic insulator 11. i118 lect, Who my bc receiving another Program With the above described method of mounting o1' Who may not Wish t0 heal my radio Programthe loop no trouble will be experienced when the Pig. 3 is nothcl' illustrative diagram Showing vehicle passes under tunnels or low obstructions one possible general electrical circuit arransewith limited clearances. At the same time, an ment wlllch may be used with the receiving Doi'- 50 eiicient means of pickup is provided. tionofthc System 0f the mventlon- Fig. 6 shows one form of coin-operated radio In the figure, 2| represents the wayside conreceiver 43 which may be employed in the system ductol' Blong the highway o1' railroad Tight-ofof the invention and which is provided with coin We? with the distance DI indicating the lateral slot 54 and timer re-set lever 55, said re-set lever extent 0f the useful induction and radiation cld 55 being turned counter-clockwise after the proper in one direction from the wayside conductors. coin is inserted in the coin slot 54. The turningl Loop 21 is shown installed in a vertical plane and of lever ss in a counter-clockwise direction winds extending parallel to the Wayside conductors 2|. any suitable timing mechanism, as well-known LOOP 2l l5 normally mounted externally on the in the art, which, after being Wound measures oil vehicle and connects to the radio-frequency input and maintains the receiving circuit in operative circuit of a multi-channel receiver i0. different condition for a given amount of time, and also channels of the receiver being tuned to the inreleases spring catch 58' which allows door 58 to coming frequencies. Such IIS Fl. F2, and F3. be opened, thereby providing access to the trans- The multi-channel output circuits of receiver ducer unit 59 attached to cord 59'. When not in il in turn are connected with multi-channel input use transducer '59 is held in place by spring clip circuits of the local transmitter or radio fre- 62. duello! empliilel'. ll- Thc multi-channel output Program selector buttons such as 51 enable the 0i the transmitter o! radiofreouency amplifier 5i user to select a program and are of the interlockis tuned t0 frequencies Such as F4. F5 and F3, or ing type so that when the selected switch is PI, F2, and F! i! the same frequency is used in pressed, any previously-operated switch is autoon and connects to loop Il, this last lloop being arranged in such manner that it exmatically restored to its "oiT position.

What is claimed as new and desired lo secure by Letters Patent of the United States is:

l. A radio program distribution system especially for moving vehicles, along a lane of trafiic,

said wayside conductor, means for separating said' carrier currents from one another, means for generating a plurality of secondary carrier currents, each'ofV said last carrier currents being modulated by the modulations of a respective one of said separated primary carrier currents, means for reradlating said secondary carrier currents over an area embracing the interior of said vehicle and a plurality of receiving means located within said vehicle, each of said receiving means being provided with program selective and electro-acoustical 'transducer means.

2. A program distribution system of the type described, including a main transmitter, a main receiver and a carrier current transmission line extending from a point closely adjacent said transmitter to a point closely adjacent said receiver, said transmitter including at least two separately modulated sources of carrier currents, a iirst unitary coupling unit receiving the outputs of all said sources and a iirst coupling loop adjacent said transmission line and receiving the output of said coupling unit, whereby the respective outputs of said carrier current sources are all impressed upon said transmission line, said receiver including a second coupling loop picking up the carrier currents from said transmission line, a second coupling unit fed from said second loop, at least two receivers fed from said second coupling unit and each tuned to a different received carrier frequency, at least two local transmitters each modulated by the output of one of said receivers, a third coupling unit fed by the output of all said local transmitters, a loop antenna energized from said third coupling unit so as to produce an induction radio field extending over a limited area, and a iinal receiver including carrier frequency selective means, electro-acoustical transducing means and a loop for picking up energy from said induction radio eld, and said carrier current transmission line including at least one lwayside conductor.

3. A multiple-channel radio transmission system eifective in serving vehicles proceeding along a lane of traine including at a central transmitting point at least two program sources, at least two main transmitters emitting energy at differingvfrequencies at said centraltransmitti'ng point, means for modulating each transmitter from a separate one of said program sources, a transmission line extending substantially parallel to the path traversed by said vehicles, single means coupling the output of all said main transmitters to said transmission line, a main receiver mounted upon 'a vehicle, said receiver comprising single means picking up the transmitted energy from said transmission line, a plurality of demodulators, each tuned to the respective frequency of one of said transmitters, single coupling means conveying energy from said pickup means to all said demodulators, a plurality of ancillary transmitters, each emitting energy at a differing frequency and each modulated from a respective one of said demodulators, an antenna of the concentrated ileld type positioned so as substantially to embrace saoid vehicle, a single coupling unit transferring the energy output of all said ancillary transmitters to said antenna, and a plurality of ancillary receivers, each including an electro-acoustical transducer and means for tuning said ancillary receiver toaselected one of the frequencies emitted by said ancillary transmitters, all said ancillary receivers being -located within the induction iield of said antenna.

4. In a carrier current radioV program distribution system of the type described and using wayside wires as carrier current transmission lines, electro-magnetic coupling means at the transmitter for impressing upon said wayside Wires a modulated carrier current, electro-magnetic means at the receiver responsive to an induction iield surrounding said wires and caused by said carrier currents viiowing in said wayside wires, means for amplifying said received/carrier current, a limited service area antenna at the receiver, means for energizing said antenna with the amplified carrier current, a nnal receiving loop antenna positioned within the eld of said limited service area antenna, tuning and demodulating means connected to said nal loop antenna, and a transducer connected to the output of said demodulating means.

5. A program distribution system for vehicles and the like, including a first generator oi modulated carrier current, means for impressing output energy from said first generator upon wayside wires, a rst receiver coupled to said wayside wires and demodulating a received portion of said carrier current, a second generator of carrier current diiering in frequency from said rst carrier current and modulated by said ilrst receiver, an inductiontype antenna fed by said second generator, a pickup loop within the eld ci said antenna, a second receiver fed by said loop and a transducer fed by said second receiver.

6. In a system of the type described, a plurality of carrier current generators, a plurality of program sources, each modulating a respective generator, a carrier transmission line receiving the outputs oi all said generators, a plurality of primary receivers coupled to said transmission line and each delivering a separate demodulated carrier current representing a. single program, a piurality oi local transmitters each modulated by K the output of a respective primary receiver, an induction4 type antenna fed by the output oi all said local transmitters, a pickup loop within the field of said antenna, and a secondary receiver fed by said loop, said secondary receiver including program selecting means, current demodulating means, an electro-acoustical transducer, and coin control switching means rendering said secondary receiver operative for a predetermined length of time for each coin inserted therein.

'1. In a radio program distribution system of the type described, a main transmitter including means' for generating a plurality of separately modulated carrier currents, a transmission line conveying said currents from said main transmitter toa receiving point, a main receiver including common pickup means and separate demodulating means for each of said carrier currents, separate local transmitters, each modulated by the output of a single demodulating means, common coupling means receiving the output of all said local transmitters, an induction loop antenna fed by said coupling means, and a plurality oi individual secondary receivers, all located within the iield of said induction loop antenna, each individual receiver including means for picking up energy from the induction eld, program selecting means, coin controlled switching means, a compartment, an earphone located within said compartment when said individual receiver is inactive, a door closing said compart ment, locking means on said door, releasing means connecting said locking means and said coin controlled switching means, whereby the insertion of a coin activates said individual receiver and unlocks said door of said compartment, and an extensible connecting cord extending from said earphone to the body of said receiver, whereby said earphone can be withdrawn from said compartment for application to the ear of the user of said individual receiver.

8. A multiple-channel radio transmission system eiiective in serving moving vehicles proceeding along a predetermined path including a plurality ol generators ot program-modulated signal carriers, a wayside wire circuit extending along said predetermined path, means for impressing output energy from said generators upon said wayside wire circuit, a ilrst receiver on a moving vehicle and coupled to said wayside wire circuit for simultaneously demodulating said plurality o! program-modulated signal carriers, a plurality of generators of carriers dli'lering in frequency from said ilrst carriers and modulated by said nrst receiver. a metallic conductive means extending within a. moving vehicle and coupled to said last mentioned generators for distributing said last mentioned modulated carriers and a selective receiver coupled to said metallic conductive means ior reproducing selected program signals.

9. A program distribution system for vehicles and the like, including a mst generator of modulated carrier signal energy, a wayside wire circuit, means for impressing output energy from said rst generator upon said wayside wire circuit, a rst receiver on a vehicle and coupled to said wayside wire circuit for demodulating received carrier signal energy, a second generator of carrier signal energy differing in frequency from said rst carrier signal energy and modulated by said ilrst receiver, a metallic conductive means within the vehicle and fed by said second generator, a second receiver coupled to said metallic conductive means and a transducer fed by said second receiver.

10. A multiple-channel radio transmission system effective in serving moving vehicles proceeding along a predetermined path including a plurality of generators of program-modulated signal carriers, a wayside wire circuit extending along said predetermined path, means for impressing output energy from said generators upon said wayside wire circuit, a first receiver on a moving vehicle and coupled to said Wayside wire circuit for simultaneously receiving a plurality oi program-modulated signal carriers, a. metallic conductive means extending within a moving vehicle and coupled to said rst receiver for distributing received program-modulated signal carriers and a selective receiver coupled to said metallic conductive means for reproducing selected program signals WILLIAM S. HALSTEAD. 

